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, MA, USA (varun.aggarwal@gmail.com) 1. Introduction The invention of radio, one of the most important inventions of the 20th century is attributed to Guglielmo Marconi of Italy. Though it is disputed whether Nikola Tesla’s patent on radio precedes that of Marconi, it is well-known that the first demonstration of radio transmission over several thousand miles was done by Marconi in the year 1901. There have been other claims of radio transmission which precede that of Marconi, but Marconi’s experiment is the only one which was not conducted in a hidden laboratory and was open for scientific scrutiny and commercialization (which he himself did).\

Figure 1: Sir J. C. Bose

There were other eminent scientists who helped Marconi and they were duly acknowledged. Prof. Fleming was a technical advisor to Marconi’s company and helped him setup his transmission station for the 1901 experiment. He had agreed to Marconi’s precondition that the complete credit for the 1901 transatlantic experiment will be that of Marconi [6]. With regard to the receiving device, Marconi claimed that it was gifted to him by his friend, Solari. The present article puts forth the fact that the receiving device used by Marconi, a mercury autocoherer was invented by Sir Jagadish Chandra Bose. Bose was the first to report this invention in his paper [9] presented at the Royal Society. Bose’s invention has clear precedence to all other claims. There is further circumstantial evidence to support this. The classic paper by Dr. P. K. Bondyopadhyay [1] published in 1998 investigates this in detail.

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It contains a two-stage spark circuit which causes multiplication of voltage to produce a high alternating current. It was designed by Prof. 2.3 The 1901 experiment Marconi alone had the strange idea that he will be able to send information riding on electromagnetic waves over the horizon. the setup of Marconi’s first Transatlantic Experiment is discussed. 1901.1 Transmission by means of modulation Heinrich Hertz’s historic experiments dealt with generation and reception of electromagnetic waves of wavelength 30 centimeters to 8 meters. Marconi established a huge transmitting antenna at Poldhu. However he didn’t conceive the idea of modulation. from which a wire came to a pole and finally to the receiver. Marconi had modified Hertz’s dipole to a monopole. which surprised the world. 2. Marconi claimed to hear the three dots representing the signal ‘S’. Marconi received the letter ‘S’ (three dots) at Newfoundland which was transmitted from Poldhu.This article is organised as follows. In Section 2. Experimental Setup for Marconi’s 1901 Experiment 2. 2. St. The receiving antenna (150m long wire [22]) was put on a kite. [3] On December 12. Other scientists disputed this. while the second stage capacitor discharges at a much higher voltage giving rise to a high alternating current. This implied generating a short duration wave for a dot. Fleming [21]. It is believed that Marconi used an end-loaded antenna at the top of the monopole to improve performance. the receiving device. The antenna used by Marconi is believed to be a cone antenna designed by Fleming [2]. Section 5 concludes the article.2 Marconi’s experimental setup for transmission of signal The transmitter used by Marconi is now referred as a spark transmitter. a longer wave for the dash and no wave for a space. 2. The receiver consisted of some kind of a ‘coherer’ and a telephone receiver to hear the signal using an earphone. Cornwall. which was at a distance of around 2000 miles.4 The receiving equipment 2
. Several periods of the supply generator were required to charge the first capacitor. To test his hypothesis. The first stage capacitor is charged by a low voltage. he stated that continent size dishes will be necessary to send audio frequency range wireless waves for voice communications [6]. Johns. A study about the different possible atenna structures Marconi may have used is given in [7]. and it is estimated that the second loop had a spark rate of just two to three sparks per second [22]. Section 4 details the controversy surrounding the coherer thus justifying its importance and provides substantial evidence that it was invented by Bose. since they believed that EM waves travel in a straight-line and they shall diverge off the surface of the earth which is spherical. In 1889.2) to send a signal to be received at Newfoundland. This current was coupled to the transmitting antenna. This is the famous transatlantic experiment of Marconi. It was Marconi who conceived the idea to ‘modulate’ electromagnetic (EM) waves using a Morse code to send information. Section 3 discusses technical details of the autocoherer. UK (Section 2.

Oliver Lodge [3]. A reasonable way to do this is to convert the current into a direct current which could then be measured. The autocoherer used by Marconi to receive the first transatlantic signal was invented by Sir J. An improved version of the coherer called the autocoherer was used by Marconi in his 1901 experiment. The device. 3. This suggests that rectification of current was required. Coherers were built by enclosing metal filings (generally silver and nickel) in a tube with electrodes dipped in it. The antenna was followed by a tuning circuit which picked up the desired frequency and fed the signal to the coherer. [15]
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. The coherer converted the AC (RF signal) to a DC signal (or a low frequency signal). which is done using diodes these days. However.1 When the RF or direct signal was applied across the coherer.
Figure 2: Receiving apparatus using a coherer
Coherer: The name coherer was coined by Prof. Both the devices are explained now.Marconi used an autocoherer to detect the electromagnetic waves. C.7] (from the order of tens of thousands to tens of Ohms).
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Interestingly. The antenna received the RF signal and provided a current at the same frequency. coherer forms the focus of this article and shall be discussed in detail in the next section. Several explanations of how a coherer worked are given in [15]. Bose invented a more accurate coherer called the Spiral Spring Receiver. Coherer is a two terminal device whose resistance drops sharply on application of a direct or alternating voltage more than a given threshold. Autocoherer: The Receiving Device The device used to detect RF signal received by the antenna during the late 1800’s is called a coherer. no diodes were available at that time and instead a ‘coherer’ was used. the filings cohered and the resistance decreased sharply [3. Bose [1]. This current had to be detected on a galvanometer or a paper tape recorder. which could then drive a Morse printer or an earphone.

don’t clearly show the biasing battery for the coherer. When the RF signal was received. Autocoherer: Autocoherers retained their initial state (‘restored’) automatically after once being subject to RF signals. 4: Coherer patented by Marconi (Brit. get it back to the initial state of high resistance. Therefore. Bose invented the Mercury Autocoherer coupled with a telephone detector in the year 18993 [9]. the coherer had to be tapped after each detection. This switched on a relay connected in series with the coherer. for continuous reception of the signal. 3 The author doesn’t have information about other forms of autocoherer which existed before this. which formed a metal-mercury contact in the second limb. Thinking that this apparent immobility of the galvanometer spot may be due to response. He used different metals in his study to understand their cohering properties. followed by instantaneous recovery. The pressure was varied by the plunger. Bose found out that the applied voltage and the pressure greatly influenced the cohering properties of the arrangement.
Fig. when a flash of radiation fell on the receiver. the secondary circuit driven by the relay also triggered a mechanical arrangement which hammered the coherer tube to decoher the particles.
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. Coherers were not accurate and the mechanical tapping system made them unreliable. it lowered the resistance of the coherer and the battery passed a small DC.
The coherer had a disadvantage that it had to be tapped mechanically to uncoher it. Patent 18105)
Bose’s arrangement had a U-tube filled with mercury. i.e. It is unclear that the dc energy came from the RF signal or the biasing battery. C. Coherers were followed by autocoherers which decohered automatically and were more accurate. the galvanometer needle being subjected to opposite impulses in Some of the references. there being the merest throb (sometimes even this was wanting) in the galvanometer spot. The relay drove a secondary circuit consisting of a Morse printer which recorded the signal [17]. The behavior of the device as an autocoherer was disclosed in his paper presented at Royal Society [9] and is quoted herein:
“Another coherer was found apparently irresponsive to radiation. For this purpose.The coherer was connected in series to a battery and the antenna which received the RF signal. 3: A drawing of the coherer designed by Bose
Fig. There was a plunger in one limb and a metal piece in the other (depicted in Figure 3).2 This is shown in Figure 2. Sir J.

L. after having obtained some very sensitive ones by means of a drop of mercury placed between cylindrical brass electrodes…” there is no mention of mercury in the paper except this one line. Claimed by Marconi. B. It may be observed that this action is close to that of a diode-detector and diode was invented some 40 years later! In [3] and [19]. The timeline of the events is given below in Table 1.rapid succession. The second set of evidence is circumstantial. Banti. The recovery was here automatic and rapid. The primary evidence is the precedence of Bose’s invention to all recorded/claimed inventions of the device. (Prof. for instance. Solari (Italy) invented the mercury coherer. Marconi conducts the famous transatlantic experiment. Claimed in an article in Italian publication L’Elettricista. editor. E. 1899 Invention/Claim David Edward Hughes uses some kind of a coherer.”
Bose’s autocoherer design used a mercury-metal interface and a telephone to detect the signal from the Autocoherer. the Mercury autocoherer was rebuilt and tested. 27. I interposed a telephone in the circuit.
Time 1878-1880 1891 Apr. Castelli (Italy) invents coherer using Mercury. the coherer restores to its original state automatically. his childhood friend and calls it the ‘Italian Navy Coherer’. His coherer uses conductors separated by mercury and telephone to detect signal. Tommasina states the following in his paper presented at Comptes Rendus (Paris): “In my researches into contact coherers. editor). He claims that the coherer was gifted to him by Solari. L’Elettricista [10] (Italian publication) sparks a controversy in regard to the inventor of the coherer used by Marconi. Banti. “On a Self Recovering Coherer and study of cohering action of different materials” [9] at the Royal Society. 1900 – Feb. [1] Tommasina states in one of his paper.
May 1. “a drop of mercury decoheres automatically…” at the Geneva Society’s Proceedings. Doesn’t use mercury. He concludes that both Castelli and Solari share credit for invention of coherer. P. Bose invented Marconi’s Wireless Detector The claim that Bose invented the autocoherer is supported by two pieces of evidence. Branly (Paris) uses a coherer. 1899
1900 Sept. To show this clearly. record of letters written by Bose talk about patent offers for his receiving device. Prof. After generating the DC for a small interval (period of RF signal detection). no tapping being necessary to restore the sensitiveness. Bose reads his paper. such that it could be recorded. each time a flash of radiation fell on the receiver the telephone sounded. The persistent debate on Marconi’s receiving device and Marconi’s elusive comments on it shows its importance in context of the 1901 experiment. The events following Marconi’s 1901 experiment are also summarized. 1901 Jan. Use of a telephone is also not stated. J. 4. No use of mercury. 1901 1902
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. UK. Marconi patents a Steel-Mercury-Carbon Coherer on his name. C. a timeline of claims of coherer invention is discussed herein. 1901 – Late 1901 Sept 1901 Dec. 1902. The action of the autocoherer is to generate a DC signal on being subject to a RF signal. The authors therein confirm the rectifying action of the autocoherer and the similarity of its transfer characteristics to that of a diode.

Solari finally gives up claim of inventing the coherer. “coherers made according to this invention consist of a drop of conducting liquid lying between two conductors… the liquid is mercury…” He reported in context of the 1901 experiment [23] “…I had substituted a telephone receiver believing that I could then detect much fainter signals. Nobel Laureate [16]: (In context of his 1901 lecture at the Royal Society.14. K. The autocoherer patented by Marconi [8] is shown in Figure 4. He
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. Bose has clear precedence to all these inventors. Marconi’s patent on the coherer is modified and the SteelMercury-Coherer is considered a gift from the Italian Navy. "Bose invented Marconi's Wireless".9. Mita Mukherjee publishes in The Telegraph. a multi-millionaire proprietor of a very famous telegraph company telegraphed me with an urgent request to meet me. IEEE publishes several other papers on J. but doesn’t give a definitive source from where he acquired it. The paper is published by IEEE. An article by Guarani [12] claims T. More than 90 years later Jan. [1. [13] P. Calcutta. The timeline clearly show that Bose was the first to publish a autocoherer which used.April 1902
June 1902
July 1902
Dec. In response he said that he is coming to meet me in person and within a short time he himself arrived with patent forms in hand. b. There is no formal publication of their work and the evidence in their favour is acknowledgment of their invention by honorable individuals.15]
Table 1: Timeline of events with context of Marconi’s receiving device. Tommasina as the inventor of the coherer used by Marconi. reproduced)
A short time before my lecture.” The only claim in the same year as Bose is by Tommasina. It cannot be concluded whether these inventors independently re-invented the device or if these were inspired/ made fraudulent claims.C. 13-26 of 3] (England).J C Bose’s letter to Rabindranath Tagore. I replied that I had no time. A mercury-metal interface. a.5. Solari categorically denies that Castelli had invented the Coherer [11]. Some appealing circumstantial evidence complementing the primary evidence is as follows:
. He talks about the Italian Navy Coherer. He claims that Lodge. 1998
S. Bondyopadhyay uncovers that Bose invented the coherer used by Marconi. P. Thompson sparks a controversy in regard to the inventor of the coherer by writing letters to Saturday Review [Ref. 1902
June 1903
1997. Telephone to hear signal. This was indeed the arrangement used by Marconi. The patent read. Bose in the same year. Solari and Castelli reportedly invented their coherers more than a year later than Bose’s publication.. The roaring debate over the receiving device shows its great significance in context of Marconi’s experiment. Ms. but denies that Tommasina had invented it. “the idea of the employment of mercury had been suggested to me by something which I had read in some English publication which I found myself unable to trace…” An article challenging the patent application filed by Marconi for the coherer is published in the Electrical Review. Marconi delivers lecture at Royal Institution of Great Britain on his transatlantic wireless signal reception. 17th May 1901. Castelli and Solari are possible inventors of the coherer. L. He claims that. whose paper has a reference to mercury. however no mention of its self-cohering property or use of telephone.

Marconi is considered and celebrated as the inventor of radio for his 1901 transatlantic experiment. .15. the Managing Director of the Marconi's Wireless and Telegraph Company [5]. that Bose had given a public demonstration of wireless transmission over a mile in 1895 and over 3 miles in 1896 in presence of the governer of Calcutta!
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. It is interesting to note that other events complement this primafacie evidence. For putting the history of science in the right perspective.I refused him.I am not getting enough time to do what I had set out to do -. it is concluded that there is prima-facie evidence to show that Bose invented the detecting device used by Marconi. Castelli. Conclusion The article covers details of concepts and equipment used in Marconi’s 1901 transatlantic experiment to proivde a context to understand the wireless detecting device. Later the book by Dunlap [4.Solari’s might be mentioning Bose: Solari’s statements in regard to coherer were not consistent with that of Marconi. It may be argued that other individuals also helped Marconi in his experiments (for instance. You donot know what money you are throwing away" etc. given his well-known work in plant physiology. Fleming). is above commercial profits.Marconi acknowledged Bose: Marconi kept changing his stance with regard to the origin of the coherer throughout his life deepening the mystery surrounding it. which Marconi personally edited. " I will only take half share in the profit -.made an earnest request to me not to divulge all valuable research results in today's lecture : "There is money in it -. 5. VIII. Hughes or Marconi had invented the coherer. p. The article then discusses the construction and working of coherers and autocoherers. It is worth noting. I am getting older . but Guglielmo Marconi and Jagadish Chandra Bose. . In regard to this. Prof. He might be mentioning Bose.18]. claim to the first patent on a solid-state device [20] and twenty-seven papers in the journal Nature. Further circumstantial evidence supports this. the author holds the view that the invention of radio should not be attributed to Guglielmo Marconi alone. 95]. Through a systematic analysis of the timeline.I will finance it" etc.let me take out patent for you. … See. ch. this hole should be now filled and reflected in the educational material used at all levels around the world. devoted one and a half page in a tribute to Bose for providing crucial support to Marconi at the critical juncture when Marconi needed it most. The precedence of Bose over all other inventors leaves no doubt that he invented the Metal-Mercury coherer. the research that I have been dedicated to doing. it may be noted that not only the contribution of these individuals is well known to the world. field of microwave engineering [14.
Here.
There are claims that Marconi’s foremost achievement was public demonstration of sending wireless signal remotely over a mile in 1896. the proprietor is believed to be Major Stephen Flood Page. Of course. This can be studied in Section VIII of [1]. Bose’s credibility needs no introduction. when he says. but they willingly left claim to the invention.4 In effect. He completely refuted that Tommasina. “the idea of the employment of mercury had been suggested to me by something which I had read in some English publication which I found myself unable to trace…”.